The present invention relates to hydraulic pumps, although other uses will be apparent from the teachings disclosed herein. In particular, the present invention relates to Bantam Duty Pumps (BDP) which can be combined with motors and other remotely-located units. When used in this manner, these BDP units provide an infinitely variable flow rate between zero and maximum in both forward and reverse modes of operation.
Pumps discussed herein are of the axial piston design which utilize spherical-nosed pistons, although variations within the spirit of this invention will be apparent to those with skill in the art and the invention should not be read as being limited to such pumps. One such prior art pump is shown in FIG. 1. The pump is a variable displacement pump 10 designed for vehicle applications. A compression spring 12 located inside each piston 14 holds the nose 16 of the piston 14 against a thrust-bearing 18. A plurality of such pistons positioned about the center of the cylinder 20 forms a cylinder block kit 22. The variable displacement pump 10 features a cradle mounted swashplate 24 with direct-proportional displacement control. Tilt of swashplate 24 causes oil to flow from pump 10; reversing the direction of tilt of the swashplate 24 reverses the flow of oil from the pump 10. The pump is fluidly connected with a motor to form a pump-motor circuit having a high pressure side and a low pressure side through which the oil flows. See generally FIG. 4C. Controlling the oil flow direction, i.e. changing the high and low pressure sides, controls the motor output rotation. Tilt of the swashplate 24 is controlled through operation of a swashplate control shaft 26 (also referred to herein as trunnion arm). The trunnion arm is connected to a slide which connects with the swashplate. Generally, movement of the trunnion arm 26 produces a proportional swashplate movement and change in pump flow and/or direction. This direct-proportional displacement control (DPC) provides a simple method of control. For example, when the operator operates a control shaft, e.g., a foot pedal, that control shaft is mechanically linked to the swashplate 24 resulting in direct control. This direct control is to be contrasted with powered control specifically indirect proportional control to move the swashplate 24. Such indirect control is often provide through the use of hydraulic and electro-mechanical devices (and combinations thereof).
A fixed displacement gerotor charge pump 28 is generally provided in BDP units. Oil from an external reservoir (such as reservoir 200 in FIG. 4C) and filter is pumped into the low pressure side by the charge pump 28. Fluid not required to replenish the closed loop flows either into the pump housing 30 through a cooling orifice or back to the charge pump 28 inlet through the charge pressure relief valve. Charge check valves 32 are included in the pump 10 and end cap 34 (cap 34) to control the makeup of oil flow of the system. A screw type bypass valve 36 is utilized in the pump 10 to permit movement of the machine (tractor, vehicle, etc.) and allow the machine to be pushed or towed. Opening a passage way between fluid ports with the bypass valve 36 allows oil to flow, thereby opening the pump-motor circuit, which then allows the motor to turn with little resistance because the vehicle wheels will not back drive the pump 10.
While such pumps are useful, they have the disadvantage of having a preferred alignment direction. More particularly, the housing 30 has a preferred alignment with the end cap. This preferred alignment direction is created by the hose coupling, or connections, between the motor 38 and the pump end cap 34 (see FIGS. 2 and 3). The placement of the system ports 40 determines the preferred alignment of the housing 30. This is particularly troublesome when one desires to control a hydraulically powered vehicle with pumps positioned on either side of the vehicle and where the control arms for the individual pumps also must be mounted to the outer sides thereof. A control arm for the left pump 10L (FIG. 2), for instance, can be conveniently connected to the trunnion arm 26 to provide control of the swashplate from the left. However, to connect a control arm to the right pump 10R, for instance, the pump must be rotated to place the trunnion arm 26 nearer to the right side of the vehicle. Costly hose fittings are then required to connect the hoses 44 to the pump 10R. Alternatively a cumbersome and costly U-shaped control linkage 46 may be connected to the trunnion arm 26 while maintaining the pump end cap in its preferred orientation, as shown in FIG. 3.
An improvement on the earlier pumps having preferred alignment is shown in FIG. 4C; the corresponding end cap 156 is shown in FIG. 14A. FIGS. 4C and 14A disclose a prior art pump wherein the end cap 156 may be connected to the housing in one of two orientations. Specifically, end cap 156 is rotatable 180xc2x0 with respect to the housing. This permits the trunnion arm 26 to be placed on opposing sides. This improved xe2x80x9csymmetric pumpxe2x80x9d has shortcomings, however, which the present invention overcomes. The advantages of a symmetric pump according to the present invention over the prior art xe2x80x9csymmetric pumpxe2x80x9d will be apparent to those with skill in the art from the teachings herein.
The present invention overcomes these and other problems by providing a pump which does not have a preferred mounting alignment. One object of the present invention is to provide a new and improved pump. A further object is to provide a symmetric pump having a symmetric housing and a symmetric end cap.
Another object of the present invention is to provide an improved hydrostatic vehicle.
Another object of the present invention is to provide means for utilizing a hydraulic pump in multiple directions without the cost of expensive fittings and accessories.
Accordingly, the present invention includes a hydrostatic powered vehicle comprising a vehicle frame and first and second hydrostatic pumps connected to the frame in first and second user selected orientations. The first pump comprises a housing having a control arm and being mounted such that the control arm extends in a first user selected direction. An end cap is connected to the housing and has a pair of case drains opening parallel to the first user selected direction. Based upon a desire hose layout, for example, a user selects one of the case drains to be plugged. The second pump similarly comprises a housing having a control arm and being mounted such that the control arm extends in a second user selected direction. An end cap is connected to the housing and has a pair of case drains opening parallel to the second user selected direction. Similar to the first end cap, a user selects one of the case drains to be plugged. Thusly, the hydraulic hose and pump control layouts may be user selected and optimized for minimum complexity.
In one embodiment of the hydrostatic powered vehicle, first and second wheels are respectively connected to first and second motors. And first and second hydrostatic pumps are respectively fluidly connected to the first and second motors. The first hydrostatic pump comprises a housing having a control arm extending in a first direction. An end cap is connected to the housing and has a pair of case drains opening parallel with the first direction and opposite each other. One of the pair of case drains is plugged based upon user criteria. The second hydrostatic pump comprises a housing having a control arm extruding in a second direction. An end cap is likewise connected to the second pump housing. The end cap has a pair of case drains opening parallel with the second direction and opposite each. One of the pair of case drains is plugged base upon user criteria. The fluid hose layout may thus be optimized for the vehicle.
The hydrostatic powered vehicle may, for some applications, comprise a vehicle frame; a first pump connected to the frame and second pump connected to the frame. The first pump comprise a housing having a control arm extending in a first direction and an end cap connected to the housing. The end cap comprises a pair of system ports opening in a second direction and a case drain opening in a third direction. Similarly, the second pump comprises a housing having a control arm extending in a direction opposite the first direction. An end cap is connected to the housing and comprises a pair of system ports opening in the second direction. A case drain opens in a direction opposite the third direction.
For some applications, the hydrostatic powered vehicle comprises a vehicle frame having first and second slides with a first wheel mounted on the frame first side and a second wheel, opposite the first wheel, mounted on the frame second side. First and second motors are respectively connected to the first and second wheels. A first hydrostatic pump is fluidly connected to the first motor via a pair of system ports. It comprises a control arm extending toward the first side and a case drain opening toward the second side. A second hydrostatic pump is fluidly connected to the second motor via a pair of system ports. It comprises a control arm extending toward the second side and a case drain opening toward the second side.
In an embodiment, the hydrostatic pump comprises an end cap having system porting; and an auxiliary charge gerotor in fluid communication with the system porting. Pressurized fluid may thus be supplied to predetermined locations.
Some embodiments of the invention are directed toward direct displacement pumps. For some applications, the direct displacement pump comprises a housing and a swashplate supported in the housing an end cap is attached to the housing and includes system ports. A charge pump is connected to the end cap. To control the swashplate, an arm extends from the housing and is positioned to act upon the swashplate. Direct displacement of the control of the pump is achieved by movement of the arm. A pump shaft is rotatably supported in housing. For some preferred embodiments, the pump shaft is a through-shaft passing through the end cap and the charge pump to extend from the charge pump. The through-shaft extending from the charge pump preferably comprises threads. And the through-shaft also preferably comprises splines in, and mating with, the charge pump. (See FIG. 23, for example.)
Other objects and advantages of the present invention will be apparent from the following detailed discussion of exemplary embodiments with reference to the attached drawings and claims.